Electrosurgery requires that the high frequency energy applied to a human or animal patient be return to the electrosurgical generator to avoid injury to the patient or surgeon. The application of a radio frequency electrical energy to a surgical site on the patient can be selected for tissue cutting, coagulation, or a blend thereof. In monopolar mode the radio frequency current that is generated by the electrosurgical generator is applied to tissue from an active electrode held by the surgeon, and is collected from a dispersive electrode or pad attached to the patient. A small contact area of the active electrode causes a high current density so that a spark enters the tissue at the surgical site. This spark causes intense localized heating, eschar, fulguration and other effects, to achieve the cutting and/or coagulation. The dispersive electrode collects the energy returning it to the electrosurgical generator to complete the electrical circuit. The dispersive electrode is of a significant size so that the energy density collected thereby is low enough to avoid any surgical or heating effect that would burn.
Burns develop when the power delivered to the tissue after passage through the body results in a high energy density at the exit because of localized tissue heating due to a high resistance connection. This situation happens when the energy is allowed to leave a human's body or animal's body at a poor dispersive electrode connection or a location other than the dispersive electrode. The later condition is called leakage. A burn from leakage can be quite severe as the patient when anesthetized will not react. The burn area is frequently covered so the doctor or surgical attendants will not see it until it is too late to take corrective action.
Another potential path for leakage burns is to the surgeon through contact with the active electrode handpiece or the conductors which supply the radio frequency, high voltage electrosurgical energy. Leakage in that circumstance may harm or burn the surgeon or one of the surgical attendants in contact with the active electrode handpiece or its supply conductor and any ground. It is for this reason that leakage or alternate path energy flow in electrosurgery are of considerable concern and efforts are made to monitor and control leakage.
An even worse condition occurs if the electrosurgical generator connection to the dispersive electrode is accidentally separated. Thus, with no direct energy path back to the electrosurgical generator, all of the power travels through any alternate grounded paths, such as through the monitoring electrodes, the surgeon and/or the surgical table. Severe burns are a possible result. At the relatively high frequencies of electrosurgical current, e.g., 500 kilohertz to 1 megahertz, stray capacitance to ground allows another ground referenced path. Furthermore, the amount of stray capacitance required to create this other significant path for ground referenced energy flow is not great.
Minimally invasive procedures include several trocars placed into the body for access to a cavity therein. One trocar could provide illumination and video, another insufflation and another minimally invasive operative instruments. Surgery through a trocar inserted opening through for example, the tissue of the abdominal wall has become an important means to minimize the extent of surgical invasion. The lessening of invasion improves the cosmetic result, shortens recovery and lowers the cost. Minimally invasive internal surgical procedures and equipment are available and in use for a variety of medical operations including gall bladder, bowel and gynecological surgery. A proper and simple instrument to selectively apply monopolar or bipolar electrosurgical effects through the opening is needed. In the minimally invasive setting, with as few as three instrument carrying openings or portals into the abdomen, the ability to treat tissue with either monopolar or bipolar systems on one handpiece is currently not feasible.
There is a wide variety of generic scissors and grasping forceps, as well as some slightly more specialized tools intended for grasping specific organs such as the gall bladder or bowel. Less invasive or minimally invasive surgical procedures are growing in frequency of use and complexity. Such procedures include: laparoscopy, thoracoscopy, endoscopy, etc.
If the surgeon had an easy way of switching between monopolar and bipolar surgery without removal of the handpiece, then the number of instruments and the time required to align the laparoscopic instrument during placement would be minimized. Monopolar electrosurgery is sometimes difficult and dangerous in a laparoscopic setting and bipolar surgery is limited with respect to the nature of the specific bipolar effectors being applied. Notwithstanding the aforesaid currently, disposable minimally invasive graspers and dissectors for laparoscopy account for millions in sales, with strong growth expected. U.S. Pat. No. 5,098,430 has a handpiece with a moveable active electrode used to selectively convert the instrument from a cutting tool when extended relative to a nozzle thereabout to a fulguration mode with the active electrode retracted relative to a nozzle thereabout. The disclosure is broadly directed to movement of the electrode although that construction is not specifically disclosed. A similar product is manufactured by Valleylab Inc of Boulder, Colo. as the model numbers E2531-6, E2532-6, E2580-28, E2581-28, E2582-28, E2583-28, E2580-36, E2581-36, E2582-36 and E2583-36 each having that have a moveable active electrode supported for axial movement coaxially within a nozzle for argon gas flow and model numbers E2718R-28, E2782R- 28, E2783R-28, E2784R-28, E2787R-28, E2788R-28, E2718R-36, E2782R-36, E2783R-36, E2784R-36, E2787R-36 and E2788R-36 each having that have a moveable active electrode supported for axial movement coaxially within an elongated shaft of a laparoscopic instrument. The disclosure and claims herein are assigned to Valleylab Inc.
U.S. Pat. No. 4,911,159 has background that discloses a wide range of handpiece switch arrangements for changing between cutting and coagulation. It is customary current practice that electrosurgical generators have an industry accepted standard spacing for the output terminals for receiving the monopolar and bipolar leads so that handpiece and leads are interchangeable. Consequently, it is preferred that the hand switching between monopolar and bipolar by on a handpiece that is interchangeable, i.e. not requiring a special generator and able to function as an accessory for existing generators.
The knowledge of skilled artisans at the time of this disclosure of a monopolar or bipolar handpiece convertible at the option of the surgeon and techniques for the change is thus negligible.